Surface Attached Polymer Networks through Thermally Induced Cross-Linking of Sulfonyl Azide Group Containing Polymers

Abstract

We report on a simple and versatile way for the modification of surfaces with thin polymer films through the thermally induced generation of surface-attached polymer networks. The system is based on copolymers, which contain a thermally reactive sulfonyl azide derivative that has been incorporated into the polymer chain during a radical copolymerization reaction. The copolymers are spin-coated from solution onto a silicon-wafer, which had been previously modified with an organosilane. Upon heating the sulfonyl azide decomposes, leading to a C-H insertion reaction and, at sufficiently high conversion, network formation. As groups in the forming network also attack the molecules of the surface-attached monolayer, the forming network becomes directly attached to the substrate surface. Following this method thin layers of polymer networks from a variety of polymers with different properties can be attached to the substrate. Furthermore, the process can be used for the generation of microstructures of polymers in hot-embossing processes. Here, cross-linking occurs during the embossing process and dimensionally stable microstructures are formed.

Surface-Anchored Poly(N-isopropylacrylamide) Orthogonal Gradient Networks

“…The SSAz and MABP cross-linkers were synthesized by employing a process similar to that described elsewhere. 28,30 The poly(NIPAAm 0.90 - co -SSAz 0.05 - co -MABP 0.05 ) copolymer was synthesized via free-radical polymerization (cf. Figure S1 in Supporting Information) initiated by AIBN.…”

“…The mechanisms of the two cross-linking reactions were investigated by Pandiyarajan et al 28 and Schuh et al 30 Concisely, benzophenone (BP) containing units absorb UV light, which results in a n– π * or π – π * transitions of carbonyl groups depending on the wavelength of the light (UV light, 360 nm, n– π *). 31 Consequently, the biradicaloid triplets, i.e., two independent radicals on carbonyl group, are formed, which can potentially abstract proton from any adjacent C–H group, resulting two carbon-based radicals.…”

“…These bonds initially do not lead to the gel, as a certain number of bonds (~one intermolecular cross-link per chain) has to be formed first. 30 An attractive feature of this system is that is can be employed on many different surfaces, for instance, polystyrene (PS) or poly(methyl methacrylate) (PMMA) supports ( vide infra ).…”

Fine neurite patterns from photocrosslinking of cell-repellent benzophenone copolymer

“…Poystyrene is not only hydrophobic but also biocompatible so that the surface-modified polystyrene (PS) is now commercially available as a substrate for cell culture. Among the various photocrosslinkable moieties such as alkyl bromide (Baek et al, 2011a,b), sulfonyl azide (Schuh et al, 2008), and cinnamic moiety (Yammine et al, 2005), benzophenone derivative was selected as a photocrosslinking agent because of the wellestablished photochemistry and proven biocompatibility (Dorman and Prestwich, 1994;Prucker et al, 1999;Dhende et al, 2011). Benzophenone is photoactive so that upon UV exposure it undergoes rapid intersystem crossing (the order of ∼10 11 s −1 ) to yield triplet exited state with almost unit quantum efficiency.…”

Malonic Acid Diazoesters for C−H Insertion Crosslinking (CHic) Reactions: A Versatile Method for the Generation of Tailor‐Made Surfaces

“…[1,16,17] While ketone-based crosslinkers can only be activated photochemically,t he cleavage of elementary nitrogen from azides or diazo moieties can occur upon photochemical and thermal activation. According to this strategy,groups with latent reactivity are incorporated as pendant groups into the polymer to be deposited.…”